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soundhead 1st January 2010 11:30 AM

very lage folded horn
 
I how to build a folded horn that play for 20 Hz to 120HZ

Size 48D X 65H X 30 D

But I do not know where to start
Ciare sw 18

Help anyone

davygrvy 1st January 2010 01:27 PM

If you start with an 18" driver you've limited yourself to how much pressure you can develop. Sd, and thus Vd, can be equaled or exceeded by numerous smaller and probably cheaper drivers. The main consideration for efficiency is how high a compression ratio you can develop. If you can get 2:1 on an 18 without ripping the cone, you're doing good. Small 8" drivers you might go as high as 6.5:1.

A horn is an acoustical transformer exchanging pressure at the cone for volumetric displacement at the mouth.

chris661 1st January 2010 02:44 PM

David, I thank you very much for that post - in one sweep, you have made me understand horns - something that has been a mystery to me for too long.

davygrvy 1st January 2010 09:27 PM

no prob.. Other types of 18" horns like the CerwinVega aren't really horns when you examine them. There's a point as you sweep down where the horn essentially disappears and all that's left is a sealed box (Vrc) which is mainly what the CV 18" horn is. I think of that just as a sealed box and made in a horn shape for marketing reasons. Ok, 120 Hz is nice and efficient probably around 106, but 30Hz is still at 91.. That's a good mid-bass, not really an efficient sub.

To get some true horn loading down to 20Hz requires a path length of around 6 meters. Mouth circumference would also need to be around 6 meters as well.

This is the part in the conversation where the compromising begins due to reality crashing in on us.

Can we assume the four cabinets you mentioned in the other thread? Can we assume these will be used outdoors in full 1/2 space (on the ground with no boundary reinforcement)? Will this be placed as a horizontal stack under a stage? By a 20Hz response, do you want it flat to 20, or some semblance of usable output there instead? 140db(SPL) @ 1M is most likely not possible given the dimensions you have... but are those dimension for one of the four cabs, or is that total space for all four?

davygrvy 1st January 2010 11:11 PM

4 Attachment(s)
Quote:

Originally Posted by soundhead (Post 2030898)
Size 48D X 65H X 30 D

Total volume of that is 1,533 liters, btw, which is nice and big. A proper tapped horn for your driver appears to achieve 125dB at 20Hz. It is excursion limited @ 26Hz to 63Vrms of drive which equates to 500W. Four cabs would get you to 137dB.

The only downside to this sim that I see is the compression ratio at 3.6:1 which I don't know if it is too high or not.

godfrey 2nd January 2010 04:09 AM

2 Attachment(s)
Here's what I get for an exponential horn (corner loaded) with:

throat area = 279 cm^2 (43 square inches)
mouth area = 4500 cm^2 (5 square feet)
length = 6m (20 feet)
back chamber = 216L (8 cubic feet)

Looks good without the back chamber, too (second pic).
Better cooling vs a bit more displacement below about 15 hz and some cancellation / interference.

edit: Oops, sorry, ignore red and blue - I forgot to erase them on second pic.

soundhead 2nd January 2010 06:51 PM

This is the design i want to put my Ciare SW 18 in

Can someone help me with the measurment please
Size is not an issue

for sub bass
Help please


http://tda-audio.users.photofile.ru/...ge/3426276.jpg

davygrvy 2nd January 2010 08:36 PM

Quote:

Originally Posted by soundhead (Post 2032384)
This is the design i want to put my Ciare SW 18 in

Path length looks to be only about 4 meters, so that's shy of 6 meters to get you to 20Hz. Good luck to you skipping the simulation aspect. And don't come back asking why it doesn't perform the way you wanted it to.

I'm done here.

soundhead 2nd January 2010 08:44 PM

Davy

I do not know nothing about hornresp.
The design i post is a design i like the measurment is off that is why i ask for help with measurment if you have any other design what you know would work best i would love to see it

sorry.

soundhead 2nd January 2010 08:52 PM

Davy if you can help me out please


Thanks


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